氟化谱中磁化率和费尔德常数的计算

计算了自旋，轨道相互作用和晶场对顺磁性物质ＰｒＦ３中Ｆｒ＾３＋离子４ｆ和５ｄ能级的影响，考虑了间接交换作用有效场Ｈγ和外磁场Ｈｅ导致的晶场基态能级的进一步分裂，最后应用三能级模型计算了磁化率Ｘ，比法拉第旋转θＦ和费尔德常数Ｖ以及它们与温度Ｔ的依赖关系，计算表明Ｐｒ＾３＋离子之间的间接交换作用对ＰｒＦ３的磁光效应有重要影响，在１１０Ｋ〈Ｔ≤３００Ｋ范围内Ｘ＾－１，Ｖ＾－１与Ｔ成线性关系，在低温与Ｔ无     

镍催化合成二元酮化物的研究

有机锡试剂与酰氯化合物的交叉偶联反应提供了合成有机酮化物的新方法。以往有机酮化物的合成常采用锂试剂和格林试剂,它们能与生成的产物酮进一步反应,对空气也很敏感。反应条件比较苛刻,常要求在低温和无氧条件下进行,同时为防止锂试剂和格林试剂在反应时发生消除副反应,对它们的纯度要求也很高。而采用有机锡试剂,则克服和解决了由格林试剂和锂试剂合成有机酮时所无法解决的问题。其主要特点是化学     

Samples Selection for Artificial Neural Network Training in Preliminary Structural Design

An artificial neural network (ANN) is applied in the preliminary structural design of reticulated shells. Major efforts are made to enhance the generalization ability of networks through well-selected training samples. Number-theoretic methods (NTMs) are adopted to generate samples with low discrepancy, i.e.uniformly scattered in the domain, where discrepancy is a quantitative measurement of the uniformity. The discrepancy of the NTM-based sample set is 1/6-1/7 that of samples with equal spacing. In a case study,networks trained by NTM-based samples are compared with those trained by equal-spaced samples in generalizing performance. The results show that both the computational precision and stability of the former ANNs are more satisfactory than those of the latter. It is concluded that the flexibility of ANNs in generalizing can be effectively increased by use of uniformly distributed training samples rather than simply piling data.More reliable uniformity should be obtained, however, through NTMs instead of equal-spaced samples.     

液化气罐焊接质量的控制

本文对液化气罐体焊缝和热影响区在高温冶金反应、结晶动力学及热循环的作用下,产生的一次结晶和二次结晶的组织形态、性能特征作了分析。实践表明,焊接夹杂和气孔是引起罐体焊缝裂纹或导致爆炸的主要原因。为此,作者提出,为了保证液化气罐焊接质量,必须从冶金和工艺两方面采取有效措施,迅速建立焊接质量监控系统,对焊接检验手段要进一步完善。     

学习生物学的记忆方法

帮助学生掌握与运用记忆的方法,是教学的一项重要任务,要提高学习生物学的效率,应该学会良好的记忆方法.学习高中《生物》的有效记忆方法有联想记忆法、观点记忆法、排除记忆法、突出重点记忆法、应用记忆法、比较记忆法等.